The world of oncology is constantly evolving as researchers continue to search for breakthrough discoveries that could lead to new treatments. One cutting-edge subset of oncology is looking toward an unexpected place: dogs.
Approximately 4 million dogs in the United States are diagnosed with cancer each year, and many of these canine cancers are the same kinds that humans are diagnosed with. Humans and dogs share many genes, and oncologists believe this could present an opportunity to make valuable discoveries that could improve outcomes for humans with cancer. This emerging field of cancer research is known as comparative oncology.
National Institutes of Health Scientists Gather Dog Cancer Data
While comparative oncology is relatively new, scientists at the National Institutes of Health (NIH) have been gathering DNA samples from dogs for nearly three decades. The geneticists have collected about 40,000 samples from all types of dog breeds.
Although the NIH focuses on studying human disease, these samples are gathered to conduct human disease research through dogs. Humans and canines share many of the same diseases. Dogs are exposed to the same environmental pollutants and are susceptible to the same cancers.
Dogs also share many of the same genes as humans, and mutations in those genes can lead to all of the health conditions humans get, such as diabetes, neuromuscular diseases, and cancer.
The NIH researchers say that studying genes in dogs is easier than in humans due to the selective breeding of dogs. The wide variety of dog breeds we see today has only existed for the past two centuries. Over these 200 years, dogs have been bred to have specific traits.
Genetic Research in Dogs with Cancer
This short, 200-year breeding timeline means that only a small number of genes are likely responsible for the major differences between different breeds of dogs. For example, a single gene can determine whether a dog has floppy or upright ears or whether its fur is light or dark. The same gene that determines ear type can also lead to a type of deafness in humans if the gene dramatically mutates.
Some dog breeds are more prone to certain types of cancer, which has allowed researchers to identify some of the cancer-causing genes. For example, Scottish terriers are approximately 20 times more likely to be diagnosed with bladder cancer compared to the average mixed breed.
Studying humans with bladder cancer is significantly more complicated. A group of humans with the disease would show different genes in different populations, along with different mutations and different environmental contributors. Analyzing a group of dogs with bladder cancer is much simpler.
Dogs can be diagnosed with common cancers found in humans, such as breast cancer, brain cancer, lymphoma, melanoma, and a type of bone cancer called osteosarcoma. Comparative oncologists hold trials that allow researchers to learn about human cancer by studying naturally occurring cancers in dogs.
Osteosarcoma in Dogs and Humans
About 10,000 dogs are diagnosed with osteosarcoma each year, compared to just 1,000 people (mostly children and young adults). This has made it difficult for oncologists to study the disease. However, research on osteosarcoma in dogs could potentially lead to breakthrough discoveries that could help people with this rare bone cancer.
In a recent 60 Minutes segment from CBS News, Anderson Cooper spoke with University of Pennsylvania professor and veterinarian Dr. Nicola Mason, who is in charge of a national network of comparative oncology trials funded by the White House’s Cancer Moonshot Initiative.
Mason showed the 60 Minutes team microscopic slides of the disease in humans and dogs. Both images looked identical, with high concentrations of purple dots that highlighted the nuclei of the cancer cells. According to Mason, even professionals cannot discern the difference between dog and human samples when examined under a microscope.
Since 2012, Mason has led trials in pet dogs for an experimental osteosarcoma immunotherapy treatment. The treatment uses a bacteria called listeria, which is one of the main causes of food poisoning. The immunotherapy treatment genetically modifies the listeria to make it much less virulent. A protein called HER2 is added, which naturally occurs in some osteosarcoma cells.
The drug is injected into the dog’s bloodstream, where it activates the dog’s immune system. This makes the dog feel sick, signaling to the immune cells that they should move throughout the body and destroy the cancer cells.
Studying Cancer in Dogs vs. Mice
Many Phase 1 clinical trials study cancers that have been injected into lab mice. Some oncologists believe that studying and treating naturally occurring cancers in dogs could be a more effective method.
The similarities in the biology of dogs and humans may make it easier to find treatments that translate to humans with cancer. Many of the cancer treatments that are proven safe and effective in dogs show promising results in humans as well. However, only about 8 percent of cancer trials using mice move to human trials.